Nanospectroscopy highlights

Exfoliated graphene crystals are not perfectly flat but can deform out-of-plane due to intrinsic and extrinsic factors. Ripples and distortions are known to be the most important sources of electron scattering in graphene, greatly affecting its transport properties. Such corrugations are also a serious obstacle to carry out angle resolved photoemission (ARPES) for probing the material's electronic structure, since this technique demands atomically flat surfaces. Combining ARPES with microprobe low energy electron diffraction makes it possible to circumvent such limitations. By measuring independently the short range roughness of corrugated suspended graphene sheets, we can distinguish corrugation effects from intrinsic lifetime broadening in ARPES,

showing that the quasiparticle lifetime scales inversely with energy. This approach is expected to be useful for probing the band structure of a variety of corrugated 2D system.

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Making angle-resolved photoemission measurements on corrugated monolayer crystals: Suspended exfoliated single-crystal graphene;
K. R. Knox, A.Locatelli, M.B. Yilmaz, D. Cvetko, T.O. Menteş, M.Á. Niño, P. Kim, A. Morgante, and
R.M. Osgood, Jr.;
Phys. Rev. B 84, 115401 (2011).
doi: 10.1103/PhysRevB.84.115401